1. Field of the Invention
The present invention relates to systems and methods for thermal treatment of industrial effluent fluids such as effluent gases produced in semiconductor manufacturing while reducing deposition of reaction products in the treatment systems.
2. Description of the Related Art
The gaseous effluents from the manufacturing of semiconductor materials, devices, products and memory articles involve a wide variety of chemical compounds used and produced in the process facility. These compounds include inorganic and organic compounds, breakdown products of photo-resist and other reagents, and a wide variety of other gases that must be removed from the gaseous waste streams before being vented from the process facility into the atmosphere.
Semiconductor manufacturing processes utilize a variety of chemicals, many of which have extremely low human tolerance levels. Such materials include gaseous hydrides of antimony, arsenic, boron, germanium, nitrogen, phosphorous, silicon, selenium; silane; silane mixtures with phosphine, argon, hydrogen; organosilanes, halosilanes, halogens and other organic compounds.
Halogens, e.g., fluorine (F2) and fluorinated compounds are particularly problematic among the various components requiring abatement. The electronics industry uses perfluorinated compounds (PFCs) in wafer processing tools to remove residue from deposition steps and to etch thin films. PFCs are recognized to be strong contributors to global warming and the electronics industry is working to reduce the emissions of these gases. The most commonly used PFCs include CF4, C2F6, SF6, C3F8, and NF3. These PFCs are dissociated in a plasma to generate highly reactive F2 and fluorine radicals, which do the actual cleaning, and etching. The products from these processing operations include mostly fluorine, silicon tetrafluoride (SiF4), and to a lesser extent hydrogen fluoride (HF), carbonyl fluoride (COF2), CF4 and C2F6.
A significant problem has been the removal of these materials from effluent gas streams of semiconductor manufacturing processes. While virtually all U.S. semiconductor-manufacturing facilities utilize scrubbers or similar means for treatment of their effluent gases, the technology employed in these facilities is not capable of removing all toxic or otherwise unacceptable impurities.
One solution to this problem is to incinerate the process gas to oxidize the toxic materials, converting them to less toxic forms. Such systems are almost always over-designed in terms of its treatment capacity, and typically do not have the ability to safely deal with a large number of mixed chemistry streams without posing complex reactive chemical risks. Further, conventional incinerators typically achieve less than complete combustion thereby allowing the release of pollutants to the atmosphere including carbon monoxide (CO) and hydrocarbons (HC). Furthermore, one of the problems of great concern in gas effluents is the formation of acid mist, acid vapors, acid gases and NOx (NO, NO2). A further limitation of conventional incinerators is their inability to mix sufficient combustible fuel with a nonflammable process stream in order to render the resultant mixture flammable and completely combustible.
Oxygen or oxygen enriched air may be added directly into the combustion chamber for mixing with the gaseous waste streams to increase combustion temperatures, however, oxides, particularly silicon oxides may be formed and these oxides tend to deposit on the walls of the combustion chamber. The mass of silicon oxides formed can be relatively large and the gradual deposition within the combustion chamber can necessitate increased maintenance of the equipment.
Accordingly, it would be advantageous to provide an improved thermal reactor unit for the combustion of highly resistant contaminates in a gaseous waste stream that provides for high combustion temperatures through the introduction of highly flammable gases for mixing with the gaseous waste stream to insure complete combustion while reducing deposition of unwanted reaction products within the thermal reaction unit.